pdfOkToAddNotes

Check to see if the PDF file allows adding notes.

int pdfOkToAddNotes(PDFHandle pdf)

This function returns zero if the PDF file is encrypted and does not
allow adding notes. The owner password can be used to circumvent this:
if a valid owner password was supplied to pdfLoadFileWithPassword
or pdfLoadMemWithPassword, this function will always return
non-zero.